List of free playground stuff for developerππ½
If you're looking for all programming tools around playground (not just free). Check this page List of playground Programming Tools

Projects and code are public by default Full-stack apps that sleep after 5 minutes Unlimited static sites that are always on Github import/export and Prettier support

SQLite Viewer Web App
A free online SQLite Explorer, inspired by DB Browser for SQLite and Airtable. Use this web-based SQLite Tool to quickly and easily inspect sqlite files on the web.
Tag: sql, playground

Codesandbox
Where teams build faster, together. Create, share, and get feedback with collaborative sandboxes for rapid web development.
Tag: IDE, playground
Free for individuals β All Platform features β Public sandboxes β Personal workspace

Trinket
Share Code from any Device. Trinket lets you run and write code in any browser, on any device.
Tag: course-builder, teaching, playground, web-development
Unlimited Basic Trinkets Python, HTML, GlowScript, Blocks and more Quick, Simple Sharing Remixing Customizable Code Editor Downloadable Code Free Activities Custom Courses

Unlimited public Pens and Collections Unlimited templates Debug view (requires log in) 1 project with 10 files

Ideone.com
Compile various programming languages online. Add input stream, save output, add notes and tags.
Tag: ide, playground

JS Bin
A live pastebin for HTML, CSS & JavaScript and a range of processors, including SCSS, CoffeeScript, Jade and more...
Tag: playground

Flatbase
Query your CSV and JSON files with SQL. Flatbase is the data science platform for developers. Upload files, write SQL, visualize results, and share with collaborators.
Tag: sql, json, api, playground
Up to 3 workspaces Share with up to 3 teammates

TypeScript Playground
The Playground lets you write TypeScript or JavaScript online in a safe and sharable way.
Tag: playground

PLAYCODE.IO
The #1 JavaScript playground and sandbox to write, run and repl it. JavaScript playground is perfect for learning and prototyping javascript sandboxes. Fast. Easy to use.
Tag: ide, playground
Unlimited projects 8 lines of code Assets storage 4 MB Deploy up to 3 websites

JSFiddle
Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor.
Tag: playground
Emmet Playground
Emmet is a powerful tool for expanding short CSS-like snippets of text, into code that would take longer to write by hand. It's pre-installed in every version of VS Code and Atom, and yet can easily go unnoticed
Tag: playground
dabblet.com
An interactive CSS playground and code sharing tool. Dabblet saves to Github gists and offers many conveniences for CSS editing.
Tag: ide, playground
Plunker
Plunker is the best tool to prototype, experiment, share and debug your ideas on the web platform. From idea to implementation, Plunker helps you build something quickly and frictionlessly.
Tag: playground, web-template

RunJS
JavaScript playground that evaluates your code as you type and gives instant feedback. Handy for prototyping ideas or trying out new libraries.
Tag: playground
Run JavaScript and TypeScript Format code Configure Babel presets and plugins Set a working directory

csplayground.io
Bring self-paced interactive coding courses to classrooms. Build your own lessons and monitor students' progress.
Tag: playground, education
All courses Create custom course Classroom management Student progress tracking 5 students

SQL Online IDE
User-friendly interface for data science. No registration for start, No DownLoad, No Install. Online test SQL script.
Tag: sqlite, mysql, database-gui, playground